Description:The muskrat
is well-named; it has musk glands near the base of the tail which give the species
a musky odor and its name. It is well adapted to its aquatic existence. Even
though it is much larger, it resembles its relatives, the voles, in that it
has a large head with small ears and eyes. It has a very dense underfur which
actually traps air and forms a waterproof barrier. Its lips seal closed behind
its incisors, which allows underwater foraging without gulping in the pond or
stream. Its pelage is dark brown to reddish-brown
on top and silvery-gray underneath. Its tail is laterally compressed to form
a rudder for swimming, and it has stiff hairs forming a fringe around its feet,
and partial webbing, which help for swimming. They are large compared to other
members of this family; total length is 18 to 22 inches (460-550 mm), tail length
is 8 to 10.2 inches (200-254 mm), and they weigh 1.5 to 4 pounds (0.7-1.8 kg).

Range:Throughout
North America north of Mexico, except portions of southwestern U.S. and Florida.

Diet:Diet
consists primarily of aquatic plants, particularly cattails, cordgrass, and
bulrushes. Also eats crustaceans and mollusks; in some areas may eat large numbers
of mussels.

Ecology:They are active year-round
and during the winter are able to swim out of their den under the ice to acquire
food. They can swim up to 180 feet (55 m) under water and can stay submerged
for up to 20 minutes. They are mainly nocturnal, but frequently seen in
daylight. Activity seems to peak twice daily: between 1600 and 1700 hours, and
between 2200 and 2300 hours. They construct dens in bank burrows or conical
houses of vegetation in shallow, heavily vegetated water. They build rooted
feeding platforms in their houses. Their home range is relatively small as they
usually do not forage more than about 35 feet (11 m) from their home site (in
marginal areas, foraging excursion areas are greater). Populations fluctuate
as density may reach up to 90 per
2.5 acres (1 ha), but it is usually much less. Individuals are generally solitary,
but several may use same general area, and in winter several may congregate
in a single den. However, territoriality is common. The species can cause damage
to river banks and the banks of irrigation canals. Young often build small nest
near their parents house shortly after becoming independent. But, in the fall,
they are often driven from the “home” pond by the parents and are forced to
disperse. They are vulnerable to predators during this time. Predators include
mink, which are known to heavily utilize muskrats, other large carnivores such
as coyotes, most likely, large raptors and humans. Their fur is very fine and
valuable and the muskrat is one of the most heavily exploited furbearers in
North America.

Reproduction:Breeding occurs in the
spring and early summer. Gestation lasts 28 to 30 days and
females produce an average of 2 to 3 litters per year. litter size varies from 1 to
12 young but in Idaho the average is about 7. Young are weaned and fairly independent
after about 1 month, and reach sexual maturity in 4 to 6 months. A high rate
of mortality exists in young.